Today, fastener systems of the type that include a threaded shank and a cap are commonly used in many areas of construction. The most common fastener design is one which includes a threaded shank, a cap, and a sealing washer. One end of the threaded shank is typically formed into a hexagonal-shaped head, and the cap includes an inner surface that includes a corresponding hexagonal-shaped recess, which creates a female component configured to mate with the male component created by the hexagonal-shaped head. The exterior surface of the cap typically includes another hexagonal-shaped projection that is larger than the hexagonal-shaped head of the shank. Prior to being used for fastening, the threaded shank and the cap are connected together, along with the sealing washer, which is positioned at the base of the cap and below the head. After the shank, the cap and the sealing washer are assembled together, they can be used for fastening together other components.
In operation, a screw gun, a socket wrench, or other tightening tool, is positioned upon the hexagonal-shaped projection of the cap, and the cap is rotated. Since the female hexagonal-shaped recess on the interior of the cap mates with the male hexagonal-shaped head of the shank, the shank is rotated and is driven into the components being affixed together when the hexagonal-shaped projection on the cap is rotated by the socket wrench. Upon full tightening, the sealing washer is compressed by the underside of the cap and/or the underside of the head, and seals about the shank.
In the construction of metal buildings, such fastener systems are the primary means for securing many of the components together. For example, such fastener systems are commonly used for holding structural members together, for securing metal sidewall panels to the structural portions of the building, and even for securing the insulation and the roof panels to the bar joists or purlins.
The exterior walls and roof of such metal buildings can be exposed to many potentially harmful environmental elements, such as sunlight, acid rain, snow, and/or sleet (depending upon the region in which the building is located) These environmental elements, among others, can cause damage such as rust corrosion, paint chalking, fading, etc.
In order to alleviate these problems, non-corrosive fasteners or non-corrosive headed fasteners are typically used. Frequently, only the cap and/or the shank head of the fastener needs to be of a non-corrosive material because only the head of the fastener and the cap are exposed to the harmful effects of the outside environment. Examples of such non-corrosive materials are stainless steel and aluminum. Zinc or another non-carbon alloy may also be used. Although these non-corrosive materials are less prone to corrosion than carbon steel, they are also softer than heat treated carbon steel. Accordingly, problems, such as fastener failures, may arise when using such softer materials in traditional fastener designs.
Most of the fastener failures result from the high torque used during tightening. One common type of failure is that in which the corners of the hexagonal-shaped head of the shank are sheared off during tightening. Such failure makes further tightening difficult. A second, and more severe, type of failure is that in which the softer metal of the hexagonal-shaped head becomes detached from its base, which is typically made of carbon steel. The area in which the base is connected to the hexagonal-shaped head is typically round. Accordingly, such a failure makes further tightening (or unscrewing) impossible. Additionally, removal of the failed fastener is also extremely difficult because of the rounded shape of the remaining shaft.
Accordingly, one object of the present invention is to provide an improved fastener system of a design that prevents the torsional failure problems discussed above.
Another object of the present invention is to provide a non-corrosive fastener, or a non-corrosive headed fastener, in which the problems associated with the use of a hexagonal-shaped head mating with a hexagonal-shaped cap interior are eliminated.
An additional object of the present invention is to provide a fastener cap in which the pattern formed on the interior thereof is of a shape other than hexagonal.
A further object of the present invention is to provide an improved fastener cap and fastener system capable of withstanding high torque.
An additional object of the present invention is to provide a high torque fastener fastener cap and fastener system that is corrosion-resistant.
A further object of the present invention is to provide a fastener and fastener system where at least the head is made of a non-corrosive material, and that is also capable of withstanding high torque.
These and other objects of the present invention are discussed or will be apparent from the following detailed description of the present invention.